Propeller



y 1930. F. w. CALDWELL 1,769,767

PROPELLER Filed Sept. 20 1924 7 [N VEN T OR 7. Caldwell M ,4 TTORNEY. v

Patented July 1, 1930 UNITED STATES PATENT. OFFICE FRANK CALDWELL, OFDAYTON,OHIO, ABSIGNOR, BY MESNE ASSIGNMENTS, TO THE HAMILTON STANDARDPROPELLER CORPORATION, 01' WEST HOMESTEAD, EENNSYLVANIA, A CORPORATIONOF PENNSYLVANIA PROPELLER Application filed September 20, 1824. SerialNo. 788,914.

This invention relates to improvements in aeronautical propellers.

The principal object of the invention consists in the provision of apropeller in which the center of gravity of all of th transversesections of the blade' are located on a straight line at right angles tothe axis of revolution of the blade and passing through that axis.

While the invention is of advantage generally as applied to propellerblades of various types, it is designed particularly for detachahle,reversible, and adjustable pitch aeronautical propellersfin whichconnection the invelition has particular utility in securing a greateruniformity in blades, and lessening the work necessary in thestandardizing and balancing operations performed in the production ofpropeller blades. At the same time blades constructed in accordance-withthis invention, whether of wood, composition, or metal, are found tooperate with less vibration and give more continued satisfactoryservice, primaril because they are inherently dynamically alanced whenthey are in static balance by reason of the manner in which the centerof gravity of any section always balances the center of gravity of thecorresponding section of an opposite blade, regardless of the pitch ofthe lades, since these centers are all on the same straight line throughthe axis of revolution.

In the accompanying drawing illustrating the invention,

Fig. 1 is a front view of a propeller blade of the detachable,pitch-adjustable type constructed in accordance with the invention.

Fig. 2 is a side view of Fig. 1 illustrating the positionment of thetransverse sections with their centers of gravity in line passingthrough the propeller axis and at right angles thereto.

Fig. 3 is a diagrammatic view looking down on a propeller blade mountedon knife edges for balancing and standardizing.

The propeller blade is shown mounted in a hub 2 and secured on a shaft3, constituting the usual extension of the engine crankshaft. The hub 2may be of any suitable or preferred form, providing for adjustment ofthe blade to vary the pitch. The clamping means 4 illustrated serves tosecure the blade in its adjusted position. The blade 1 has its shanksuitably held in the hub 2 and is laid out on a longitudinal axis y-y atright angles to the axis a:a: of the shaft 3, corresponding to the axisof revolution of the propeller. The axis g y passes through the axis Has shown in Fig. 1 and is at right angles thereto, as shown in Fig. 2.The center of gravit of each of the transverse sections of the lade lieson the line of the axis y-y. Sections a-a, bb, c0, and 0ld are shown inFig. 2 so located with reference to the axis y-y.

The advantage derived in this design, aside from the fact that thelikelihood of vibration due to slight irregularities and uncompensatedmoments in the blade is minimized, resides in the fact that largequantities of blades of the detachable type may be produced of souniform a character as to be readily interchangeable and replaceable.This is due to the fact that in the balancing and standardizing of ablade, the described location of the center of gravity of all of thesections renders it easy to locate and properly compensate for any partsout of balance. Thus, as shown in Fig. 3, a particle represented by thedot (1 represents a part out of balance. When the blade is tested forhorizontal and vertical balance, this particular part, if compensatedfor in the horizontal balance, would nevertheless throw the blade out ofbalance when the blade is rotated, say for example, to the dotted lineposition which is approximately 90 from the full line position. In thisposition the particle now represented by the dot at is oil the axis ofthe shaft 3, which is free to roll on the knife edges represented at 6and 7. A balancing particle b is therefore necessary on the oppositeside of the axis. By displacing the blade 90 from the first position ofbalance, a very sensitive balance of all unbalanced particles issecured, since the unbalanced particles are thereby given a maximummoment arm. If a blade constructed in accordance with my invention is inperfect balance statically, it will then be also in perfect dynamicbalance as a result inherent in the construction; since 'ustable all ofthe centers of gravity of all the sections of the blade will al be onthe same strai ht line through the axis of rotation at e to that axis.This will be true regardes of the an 1e to which the blade is adjusted.The lade will therefore operate without appreciable vibration withinthe 1. An aeronautical propeller comprising:

a blade-clampin hub, and a pluralit of similar detachable lades adaptedto rotatably mounted with respect to the hub to permit pitch-adjustment,each blade having its mass so distributed throughout that its axis ofrotation with respect to the hub passes through the centers of mass ofall transverse sections of the blade.

2.- An aeronautical propeller comprisin a blade-clampin hub, and alurality of setachable pitch-adjustable lades radiall disposed relativeto the ropeller axis, eac blade having its mass so istributed throughoutthat the centers of mass of all cross sections lie in a line whichpasses through the propeller axis, whereby to maintain the dynamicbalance of the blades in operation regardless of pitch-adjustmentthereof.

3. An aeronautical propeller comprisin a blade-clamping hub and separateremova 1e pitch-adjustable blades constructed and mounted with equal andsimilar sections at equal distances respectively from the axis ofrevolution of the blades, each blade having the centers of mass of allof its cross sections lying on a line that passes through the propelleraxis.

4. An aeronautical propeller comprisin a blade-clampin hub and separateremova le pitch-adjustab e blades constructed and mounted with equal andsimilar sections at equal distances res ectively from the-axis ofrevolution of the lades, each blade having the centers of mass of all ofits cross sections lying on a line that passes through the propelleraxis at right angles thereto.

5. An aeronautical propeller comprisin a blade-clampin hub and twodiametricall oppositel posltioned symmetrical-pitch-ad lades carried bsaid hub, said lades being constructed wlth e ual and similar sectionsat equal distances rom the propeller axis, res ectively, and soproportioned and positione that a straight line passes through thecenters of mass of all cross sections of the two blades and through thepro peller axis.

6. An aeronautical propeller comprising a blade-clamping hub and twodiametrically oppositel positioned s etrical pitch-a 'ustable bladescarrie by said hub said lades being constructed with egual and similarsections at equal distances rom the propeller axis, respectively, and soroportioned and positioned that the axis 0 rotation for pitch-adjustmentcomprises the centers of mass of all cross-sections of the blade.

7. In aeronautical pro llers, a separate blade having a shank a apted tobe rotatively engaged by a hub member, said blade having the center ofmass of all of its cross sections lying in the axis of its rotation withres ect to the hub.

n testimonlg whereof I aflix m si ature.

RANK W. CAL LL.

